Feeder



Sept. 19, 1939. w. M. FULTON FEEDER Filed Jan. 31, 1939 2 Sheets-Sheet 1Sept. 19, 1939. w. M. FULTON FEEDER Filed Jan. 31,1939 2 Sheets-Sheet 2u WIIIIIIIII 'IIIIIIIIII alllllzzdllllllllllllilllllllllllllliIlllluIIlnuIIllllm V III/m i Patented Sept. 19, 1939 UNITED STATESPATENT OFFiCE FEEDER Application January 31, 1939, Serial No. 253,930

Claims.

This invention relates to feeders, and especially to feeders used tohandle lumpy solids such as coal, coke, crushed stone and the like. Theinvention is particularly described hereinafter in 5 connection with afeeder whereby the material being fed is elevated from a lower to ahigher level. For example, in the case of over-feed stokers, where coal,coke, or other lumpy fuel is fed into a combustion chamber anddistributed over the top of the grates, the fuel is usually elevated andfed onto a fiat surface at the front of the combustion chamber and blownfrom there over the fuel bed by means of compressed air or steam. Herethe feeder is required to elevate the fuel and deposit it on the surfacefrom which it is blown into the combustion chamber. It will beunderstood, however, that feeders embodying the invention may also beUsed to feed fuel and other materials at desired inclinations orhorizontally.

Feeders of this type conventionally embody a screw operating in a pipeor casing, the fuel or other material being fed laterally into the pipeas by means of a hopper. Such feeders as heretofore constructed possessa number of defects. For satisfactory results the screw has to fitfairly snugly into the pipe so that the space between the outer surfaceof the screw and the inner surface of the pipe is quite limited. Hence,feeders of this type can only handle materials which are sufficientlysoft to be crushed by the screw when particles are caught between thescrew-flights and the entrance end of the pipe. Particles of foreignmatter, such as pieces of iron, wood, flint, etc., which find their wayinto coal during its handling from mine to consumer, become caughtbetween the flights of the screw and the entrance to the feed-pipe andthereby render the feeder inoperative.

To make the feed-screw and feed-pipe of sufficiently rugged dimensionsand of sufliciently hard material to handle such foreign matter wouldexcessively increase the cost of manufacture, and consequently variousexpedients have been resorted to in an effort to overcome thesedifficulties. For example, a shearing pin has been used in the screwdriving mechanism which is sheared whenever the feed screw becomesclogged and offers undue resistance to rotation. In such cases, however,the feeder cannot be put back into operation without, first, removingthe cause of the trouble, and second, replacing the sheared pin. Theseare unpleasant and timeconsuming tasks, especially where the feeder isused on a domestic stoker and the house-owner himself is called upon todo the work without adequate tools and with limited experience inmatters of this kind. Another device consists in operating thefeed-screw by means of a hydraulic motor, with a relief valve in the oilpressure line feeding process until the foreign matter can be removedfrom the feeder and at best are quite unsatisfactory makeshifts. In sometypes of feeders, moreover, if the feeder remains idle for aconsiderable length of time combustion works its way around the deliveryend of the feedscrew and fuses clinker around the screw so tightly thatthe feeder must be disassembled and the clinker cleaned out. This latteroperation not only interrupts the flow of heat from the heater, but,generally, necessitates starting the fire entirely anew.

It is an object of the present invention to avoid the foregoingdifiiculties and to provide a feeder of the type characterized abovewhich is simple and inexpensive and at the same time capable of handlinglumpy material without amming.

Another object is to provide novel means for insuring passage ofmaterials through the feeder while eliminating the usual closelysurrounding pipe or casing. 1

Another object is to provide continuous feeder operation in case ofobstruction at its delivery end by by-passing the material fed throughthe feeder.

A further object is to provide uniform passage of material through thefeeder together with regulation of the rate of discharge of materialfrom the feeder.

Other objects will appear hereinafter as the description of theinvention proceeds.

One embodiment of the invention has been illustrated in the accompanyingdrawings, but it is to be expressly understood that said drawings arefor purposes of illustration only and are Fig. 1 with the side plateremoved to show the interior construction;

Fig. 4 is a horizontal sectional view of the feeder shown in Fig. 1;

Figs. 5 and 6 are detail views showing the screw-flights of the feeder;and

Fig. 7 is a detail view showing means. for mounting the screw-flights ona drive shaft.

The feeder as illustrated in the drawings may be used to elevate coalfor an overfed stoker, although as stated above, materials may be fed inany desired direction by inclining the screws at an angle or arrangingthem horizontally. Broadly stated, the feeding mechanism comprises amain feed screw, a co-acting screw having an axial baflie flangecooperating with the flights of the main screw, and a retention platefitted around a portion only of the circumference of the main screw.Preferably the two screws rotate in the same direction, that is to say,both rotate clockwise or both rotate counter-clockwise, and in this casethe two screws are both threaded alike, that is to say, both haverighthand threads or both have left-hand threads. Another importantfeature of the present invention is that the retention plate does notcompletely surround the main screw but on the contrary leaves a portionof the circumference of said screw exposed with the edges of theretention plate extending parallel to the axis of the screw, the exposedportion of the circumference being at least suflicient to admit entranceto the screw, in a direction approximately perpendicular to the screwaxis, of the largest lump of material being fed. Hence there is no edgeperpendicular or approximately perpendicular to the axis of the screwagainst which lumps of material can be forced in such a way that thescrew must shear these lumps apart.

A feeder embodying these features is illustrated in the drawings. Themain screw I cooperates with a second screw 2 having an axial baffleflange 3 and with a retention plate 4. The screws are threaded alike andare rotated in the same direction and at the same speed in any suitablemanner as by gear wheels 5 and 6 secured to driving shafts I and 8 ofscrews I and 2 and interconnected by an idler gear 9. These gears may bedriven in any suitable manner as by the bevel gear Ill on the gear 5which meshes with a second bevel gear II on a drive shaft I2.

Each screw may be made as a single unit, or may be made up of a numberof separate sections so that screws of different lengths can beassembled from a stock of individual flights. Further, it is desirablethat the edge of the flange 3 and the feeding surface of screw I rotatein actual contact or substantially so, and hence screw 2 is preferablycomposed of individual flights mounted on the shaft 8 in such a mannerthat each individual flight may slide lengthwise on the shaft whilebeing forced to rotate with the shaft. As shown in Fig. 6, each of theseflights comprises a central hub portion I3 and a spiral portion I4 tothe outer edge of which is joined the axial baffle flange 3. The hub I3has a keyway I5 therein and the shaft 8 on which these flights aremounted is provided with a suitable spline or key which loosely engagesthe key-ways I5 of the flights so that the latter may slide lengthwiseon the shaft but are forced to rotate with the shaft. In many cases itis sufficient to have key-ways in none but the top and bottom flightsand have these two flights drive the intermediate ones through contactat the ends of the flanges 3. Spaces I6 between flights leave each onefree to adjust itself lengthwise of the shaft independently of theneighboring flights.

As shown herein, main feed screw I is also made of individual flightsmounted on the shaft '1. As shown in Fig. 5, each of these flightscomprises a central hub portion I! having a key-way I8 therein and aspiral portion I9. However, radial elements of the top surface of thisspiral portion I9 are not straight lines projecting at I right anglesfrom hub H, as is true of conventional conveyor screws, nor does thissurface possess the form of threads found on ordinary machine screws andbolts, but, on the contrary, it is made to conform substantially to thecurve described by the lower edge of the flange 3 between its point ofintersection with the periphery of screw I and a point adjacent thescrew hub I'I. As will be seen in Fig. 5, the top surface of screw Icurves upward as it approaches hub I'I, rapidly increasing in curvatureas its proximity to hub II increases. The flights of screw I may each beattached to the shaft, or the top and bottom flights may be attached tothe shaft and used to drive the intermediate ones through contact of theedges of the spiral portion IS), the hubs I'i snugly abutting againsteach other. When assembled on its driving shaft I the main screwtherefore operates as a single unit, but

due to the spaces IS the flights of screw 2 are free to adjustthemselves lengthwise of driving shaft 8 so that they will ride upon thecompanion flights of screw I and will automatically adjust themselvesfor wear and thus continually maintain a tight closure between thecontacting surfaces of the respective flights.

In the case of very large screws where the flights of screw 2 aremassive and might consequently produce undue friction in their contactwith the flights of screw I, the flights of screw 2 may be resilientlysupported to reduce the friction. One method for accomplishing this isillustrated in Fig. 7. The hubs of adjacent flights of the screw 2 arecounterbored to form recesses 20 into which are inserted coil springs2|, the lower ends of the springs abutting against collars 22 which aresuitably secured to shaft 8 as by means of pins, said collars having anoutside diameter approximately equal to the inside diameter of thecounterbored spaces 20 but with sufficient clearance to permit theflights to slide freely along the shaft. The hub portions above therecesses 20 are provided with key-ways I5 as above described in whichare slidably fitted keys 23 which in turn are made fast in keyways 24 inshaft 8. This construction permits the flights to slide freely in thedirection of the axis of shaft 8 but forces them to rotate with saidshaft, and they are guided in a true rectilinear movement by the hubportions which slide on the shaft 8, and by the collars 22 which fitslidably inside the recesses 29. The springs 2| exert a resilient forcetending to raise the flights and by selecting springs of suitable lengthand resilience the pressure of the flights on the screw I can berelieved to the desired extent while at the same time the springs permitlongitudinal adjustments of the flights when in operation.

As shown more clearly in Figs. 3 and 4, the

retention plate 4 may be suitably mounted by attaching one edge, bywelding or otherwise, to a frame member 25. The other edge of theretention member, which may be termed its leading edge in the directionof rotation of screw I, flts snugly into the axial line through thepoints of intersection of the helical peripheries of screws l and 2. Atthe discharge end the leading portion of the retention member is cutaway to provide an opening 26 through which material is discharged fromthe feeder, and atrough or spout 21 of any desired shape and length isfitted into the opening '26 for conducting the material to any desiredplace. Opening 26 and spout 21 are thus placed at a lower level than thetop of the remainder of the retention member 4. This not only insuresthat the material will be dis charged through the spout 2'! withoutdanger of overflowing the top of member 4, but as will be presentlypointed out it further insures that, in the event spout 2'! becomesclogged or the flow therethrough is restricted, surplus material will bedischarged over the edge of the spout and allowed to fall by gravityback to the source from which it is being fed without interfering withthe otherwise normal functioning of the feeder.

The feeder mechanism thus far described may be connected to or used witha hopper or storage bin, etc., in any convenient way. As illustrated inthe drawings, the feeding mechanism is installed in a hopper 28 having alid 29 hinged at 3!! to stationary parts of the hopper so that it can beraised to permit charging fuel into the hopper. As shown, a portion 3|of the hopper extends upward above lid 29 and other portions of thehopper to house the upper part of the feeding mechanism, and partitionwalls 32 and 33 extend down inside the hopper to within a short distanceof the bottom 34 and, in conjunction with the two outside walls 35 and35 of the hopper, constitute an inclosure for the lower part of thefeeding mechanism. The feeding mechanism is thus housed in a casing towhich fuel is delivered at its bottom by the hopper. In this way thehop-per door 29 can be placed as low as desired so that fuel does nothave to be lifted to an inconvenient height, and at the same time thefuel can be delivered at any desired height within practical limits byadding flights to the feeder screws. The frame member 25 is suitablyattached as by means of rivets to the bottom 34 and top 3! of the hopperwhich also provide suitable bearings for the shafts l and 8 of thescrews. A frame member 38 connects the top and bottom of the hopper onthe side opposite the member 25. The frame side members 25 and 38, andthe bottom 34 and top 31 of the hopper which in effect constitutecrossp-ieces for the side members, thus carry the entire-feedermechanism and comprise therewith a feeder unit which can be installed inany hopper, bin, etc. The side walls of the hopper may thus be made ofrelatively thin sheet metal.

The operation of this improved feeder is as follows:

Fuel such as coal or coke is placed in hopper 28, filling it to the topor as nearly so as desired. Partition walls 32 and 33 allow fuel to flowby gravity past their lower edges and into and around scr ws 5 and 2,but without completely submerging the screws which might cause irregularfeed. The bottom flights. of the screws are preferably brought to afairly sharp edge so as to scrape the surface of the hopper bottom 34.As the screws rotate, being driven by the gearing described above, screwi takes in fuel at its bottom and at that portion of its circumferencewhich is left openly exposed and the fuel thus taken in is carriedaround until it is confined by the retention plate 4 so that it cannotslide off of the revolving flights. At the same time screw 2 carriesmaterial to the screw l at its open side.

It will be noted that the edge of the retention member 4 where the fuelenters the screw I is disposed in a direction parallel with the axis ofrotation of the screw and not perpendicular thereto, so that any lumpsof material which may be caught between the screw and this vertical edgemerely slide along the edge until they become free from the screw and donot have to be sheared. For this reason the feeder is nonclogging and noshearing pins or other safety devices are required. Once the fuel hasentered the screw, it is forced upward and around until it contacts therevolving baffle flange 3 of screw 2, whereupon it is confined within aspace bounded by retention plate 4 and flange 3 from which it cannotescape. It is then carried upward by the action of screw 1 until itreaches opening 26 whereupon it is swept off through this opening intospout or trough 2'! by the revolution of screw 2.

Fuel is thus being continually elevated from the bottom of screw I anddischarged through trough 2'1. The construction is such that if spout2'! should for any reason become clogged so that fuel would fail to passthrough it, then screw I would carry the fuel on up and discharge itover the top of the edge of the spout 21 and allow it to fall by gravityback into the hopper. If the fuel should contain lumps too large to dropthrough the open space between the screws and the hopper walls, thenthis space may be enlarged to any desired size by locating screw 2 awayfrom hopper wall 35, all other parts of the feeder remainingundisturbed. As material drops through this space to the hopper bottomit is carried around by screw 2 and delivered to screw l to be again fedupward. As long as opening 26 is clogged or restricted, fuel will becarried up and dropped back, thus merely circulating it, and no damagewill be done to the feeder.

Overfeed stokers are usually engineered by combustion experts whopredetermine the amount of fuel required per hour, and variations fromthis requirement do not have to be made with great frequency nor withinvery wide limits. When, therefore, the feeder just described is used forfeeding fuel to an overfeed stoker, necessary variations in rate of feedcan be obtained by any well known device for varying the speed of thedriving shaft. When, however, this feeder is: used for handling othermaterials where more fr quent changes in rate of feed are required, andthe material must be metered more accurately, this can be accomplishedvery simply and effectively by any suitable means for regulating therate of discharge of materials through or from the spout 2?. In the formshown in Fig. 1, a gate 39 is provided in spout 2?, said gate sliding inways 40 and being operated by a screw 4i threaded in a bracket 42suitably attached to the top of the spout 21. The screw ll has asuitable swivel connection with the gate 39 and. as here shown extendsfreely through the upper part of the gate into an opening 43 where itterminates in a head or disk 44. As the screw is rotated, gate 39 iscarried up or down with it, thereby enlarging or reducing the size ofthe opening through the spout 21 and increasing or decreasing the amountof material discharged per hour through the spout 21. This simple andexpeditious method of regulating the rate of feed is made possible bythe fact that, as previously pointed out, the feeder will continue todeliver material to spout 21, and such portion of this material as doesnot pass out freely through the spout is carried on up above the openingand discharged back into the hopper.

Since screws I and 2 are not confined within closely fitting housings,but on the contrary are open on all sides except for the fractionalportion of screw I inclosed by retention plate 4, this feeder willhandle any material whose size does not exceed the pitch of the flights.If any lumps of material greater in size than the pitch of thescrew-flights are placed in the hopper, the feeder automatically refusesto take hold of them and they remain in the hopper after all material ofproper size has been fed out. It is therefore evident that the feedercannot become injured by foreign matter at either its intake ordischarge ends. Furthermore, since the feeder screws l and 2 are of theopen type, friction between the screw and the fuel is greatly reduced,and correspondingly less power is required.

It is to be further noted that since screws l and 2 rotate in the samedirection, and since the peripheral speed of the flange 3 is greaterthan the peripheral speed of the hub or adjacent body portion of screwI, there is a constant tendency for the material being fed to be drivenaway from the line of contact between the periphery of screw 2 and thehub, or body, portion of screw I, instead of being drawn into it. Hencethe wedging and jamming of material between the screws, which is adefect in other feeders, is completely obviated in the presentinvention.

While only one embodiment of the invention has been described andillustrated in the drawings, it Will be understood that the invention isnot restricted to this embodiment, and that various changes may be madein the form, details of construction and arrangement of the partswithout departing from the spirit of the invention, many of whichchanges will now be apparent to those skilled in the art. Reference istherefore to be had to the appended claims for a definition of thelimits of the invention.

What is claimed is:

1. Feeding mechanism comprising a pair of intermeshing screws threadedin the same direction, means for rotating said screws in the samedirection and at the same speed, one of said screws having an axiallyextending periphery which rotates with its edge substantially in contactwith the feeding surface of the other screw, and a retention memberpartially surrounding said other screw with its edges parallel to thescrew axis, said retention member terminating with its leading edgesubstantially in the axial line through the points of intersection ofthe helical peripheries of said screws.

2. Feeding mechanism comprising a pair of intermeshing screws threadedin the same direction, means for rotating said screws in the samedirection and at the same speed, one of said screws having an axiallyextending periphery forming a baffle which rotates with its edge incontact with the feeding surface of the other screw, said feedingsurface being shaped to conform to the edge of said baffle substantiallyalong a line extending from a point adjacent the hub of said other screwto the point of peripheral intersection of said screws, and aretention.- member partially surrounding said other screw with its edgesparallel to the screw axis, said member terminating with its leadingedge substantially in the axial line through the points of intersectionof the helical peripheries of said screws.

3. Feeding mechanism comprising a pair of intermeshing screws threadedin the same direction, means for rotating said screws in the-samedirection and at the same speed, one of said screws being mounted foraxial movement and having an axially extending periphery which rotateswith its edge in contact with the feeding surface of the other screw,and a retention member partially surrounding said other screw with itsedges parallel to the screw axis, said member terminating with itsleading edge substantially in the line through the points ofintersection of the helical peripheries of said screws.

4. Feeding mechanism comprising a pair of intermeshing screws threadedin the same direction, means for rotating said screws in the samedirection and at the same speed, one of said screws comprising sectionsmounted for individual axial movement and having axially extendingperipheries which rotate with their edges substantially in contact withthe feeding surfaces of the other screw, and a retention memberpartially surrounding said other screw with its edges parallel to the.screw axis, said retention member terminating with its leading edgesubstantially in the axial line through the points of intersection ofthe helical peripheries of said screws.

5. Feeding mechanism comprising a pair of intermeshing screws threadedin the same direction, means for rotating said screws in the samedirection and at the same speed, one of said screws compriisng sectionsmounted for individual axial movement and having axially extendingperipheries which rotate with their edges substantially in contact withthe feeding surfaces of the other I screw, resilient means forsupporting said sections at least in part, and a retention memberpartially surrounding said other screw with its edges parallel to thescrew axis, said retention member terminating with its leading edgesubstantially in the axial line through the points of intersection ofthe helical peripheries of said screws.

6. Feeding mechanism comprising a pair of intermeshing screws threadedin the same direction, means for rotating said screws in the samedirection and at the same speed, one of said screws having an axiallyextending periphery which rotates with its edge substantially in contactwith the feeding surface of the other screw, a retention memberpartially surrounding said other screw with its leading edgesubstantially in the axial line through the points of intersection ofthe helical peripheries of said screws, the leading portion beingshorter than the remainder of said member at the discharge end of saidmechanism to provide a discharge opening, and a; discharge conduitcommunicating with said opening.

7. Feeding mechanism comprising a pair of intermeshing screws threadedin the same direction, means for rotating said screws in the samedirection and at the same speed, one of said screws having an axiallyextending periphery which rotates substantially in contact with thefeeding surface of the other screw, a retention member partiallysurrounding said other screw with its leading edge substantially in theaxial line through the points of intersection of the helical peripheriesof said screws, the leading portion being shorter than the remainder ofsaid member at the discharge end of said mechanism to pro- Vide adischarge opening, a discharge conduit communicating with said opening,and means for regulating the rate of discharge of material through saidconduit.

8. Feeding mechanism comprising a pair of intermeshing screws threadedin the same direction, means for rotating said screws in the samedirection and at the same speed, one of said screws having an axiallyextending periphery which rotates with its edge substantially in contactwith the feeding surface of the other screw, a retention memberpartially surrounding said other screw with its leading edgesubstantially in the axial line through the points of intersection ofthe helical peripheries of said screws, the leading portion beingshorter than the remain der of said member at the discharge end of saidmechanism to provide a discharge opening, a discharge conduitcommunicating with said opening, and an adjustable gate for regulatingthe effective cross-sectional area of said conduit.

9. Apparatus of the class described comprising a casing, means fordelivering material to be fed to one end of said casing, feedingmechanism in said casing comprising a pair of intermeshing screwsthreaded in the same direction, means for rotating said screws in thesame direction and at the same speed, one of said screws having anaxially extending periphery which rotates with its edge substantially incontact with the feeding surface of the other screw, and a retentionmember partially surrounding said other screw with its edges parallel tothe screw axis, said retention member terminating with its leading edgesubstantially in the axial line through the points of intersection ofthe helical peripheries of said screws, the leading portion beingshorter than the remainder of said member at the discharge end of saidmechanism to provide a discharge opening, and a discharge conduitcommunicating with said opening and extending outwardly of said casing.

10. Apparatus of the class described comprising a casing, means fordelivering material to be fed to one end of said casing, feedingmechanism in said casing comprising a pair of intermeshing screwsthreaded in the same direction, means for rotating said screws in thesame direction and at the same speed, one of said screws having anaxially extending periphery which rotates with its edge substantially incontact with the feeding surface of the other screw, and a retentionmember partially surrounding said other screw with its edges parallel tothe screw axis, said retention member terminating with its leading edgesubstantially in the axial line through the points of intersection ofthe helical peripheries of said screws, the leading portion beingshorter than the remainder of said member at the discharge end of saidmechanism to provide a discharge opening, a discharge conduitcommunicating with said opening and extending outwardly of said casing,and means for regulating the rate of discharge of material through saidconduit.

11. Apparatus of the class described comprising a receptacle formaterial to be fed, feeding mechanism in said receptacle and spaced fromthe walls thereof, said mechanism comprising a pair of intermeshingscrews, one of which has an axially extending periphery rotatingsubstantially in contact with the feeding surface of the other screw, aretention member partially surrounding said other screw with its edgesparallel to the screw axis and its leading edge substantially in theaxial line through the points of intersection of the peripheries of saidscrews, the leading portion of said retention member adjacent thedischarge end of said mechanism being shorter than the remainder toprovide a discharge opening, and a discharge conduit communicating withsaid opening and extending outwardly of said receptacle, wherebymaterial is fed to said discharge conduit and excess material isdischarged over the top of said retention member into the space betweensaid mechanism and the walls of said receptacle.

12. Apparatus of the class described comprising a receptacle formaterial to be fed, feeding mechanism in said receptacle and spaced fromthe walls thereof, said mechanism comprising a pair of intermeshingscrews, one of which has an axially extending periphery which rotatessubstantially in contact with the feeding surface of the other screw, aretention member partially surrounding said other screw with its edgesparallel to the screw axis and its leading edge substantially in theaxial line through the points of in-. tersection of the peripheries ofsaid screws, the leading portion of said retention member adjacent thedischarge end of said mechanism being shorter than the remainder toprovide a discharge opening, and a discharge conduit communicating withsaid opening and extending outwardly of said receptacle, and means forregulating the rate of discharge of material throughsaid conduit,whereby material is fed to said discharge conduit and excess material isdischarged over the top of said retention member into the space betweensaid mechanism and the walls of said receptacle.

13. In a feeder, the combination of two intermeshed screws, on oneacting as a feeder screw and the other as a baflie, and a retentionmember partially surrounding said feeder screw, said feeder screw beingopen on its intake side throughout the entire distance through whichmaterial is fed, whereby shearing of lumps by the feeder screw isobviated.

14. In a feeder, the combination of two intermeshed screws, one actingas a feeder screw and the other as a baffle, and a housing partiallysurrounding the feeder screw with its edges lying approximately in thedirection of'travel of the material fed, whereby shearing of lumps bythe feeder screw is obviated.

15. In a feeder, the combination of a feed screw, a baffle screwcoacting therewith comprising a plurality of individual flights, andmeans for mounting said flights for rotation in unison but for freeindividual movement in the direction of the axis of rotation.

WESTON M. FULTON.

